The subject matter disclosed herein relates to knock sensors, and more specifically to knock sensors suitable for sensing engine knock and piston slap in combustion engines.
Combustion engines typically combust a carbonaceous fuel, such as natural gas, gasoline, diesel, and the like, and use the corresponding expansion of high temperature and pressure gases to apply a force to certain components of the engine, e.g., piston disposed in a cylinder, to move the components over a distance. Each cylinder may include one or more valves that open and close correlative with combustion of the carbonaceous fuel. For example, an intake valve may direct an oxidizer such as air into the cylinder, which is then mixed with fuel and combusted. Combustion fluids, e.g., hot gases, may then be directed to exit the cylinder via an exhaust valve. Accordingly, the carbonaceous fuel is transformed into mechanical motion, useful in driving a load. For example, the load may be a generator that produces electric power.
Knock sensors can be used to monitor multi-cylinder combustion engines. A knock sensor can be mounted to the exterior of an engine cylinder and used to determine whether or not the engine is running as desired. Sometimes a knock sensor detects piston slap and mistakes the piston slap for engine knock. When this occurs, the engine control system, which is connected to the knock sensor, may attempt to make adjustments to eliminate the engine knock it believes is happening, but is really piston slap. These adjustments may induce engine knock or otherwise make the engine run in an undesirable way. Thus, it would be desirable to have a way to distinguish piston slap from engine knock.